1. Field of the Invention
This invention relates to an ultraviolet (UV) absorber composition and a resin composition.
2. Background Art
A UV absorber has been used in combination with various resins to impart UV absorbing properties to the resins. UV absorbers include inorganic UV absorbers and organic UV absorbers. Inorganic UV absorbers, such as disclosed in JP-A-5-339033, JP-A-5-345639, and JP-A-6-56466, are excellent in durability including weatherability and heat resistance but provide limited choice because the absorption wavelengths depend on the band gap of the compound. No inorganic UV absorbers are capable of absorbing long wavelength UV light called UV-A irradiation having wavelengths around 400 nm, or inorganic UV absorbers capable of absorbing UV-A irradiation also absorb visible light and are therefore accompanied by coloration.
On the other hand, organic UV absorbers offer broad freedom of design of their structure. Hence, organic UV absorbers having various ranges of absorption wavelengths are provided through structural design.
A variety of organic UV absorbers have thus been studied. For example, JP-T-2002-524452 discloses triazole UV absorbers, of which those having an absorption maximum in the UV-A region have poor light resistance and reduce in UV light shielding effect with time.
To address this problem, it has been proposed to use a combination containing a UV absorber having UV light shielding effect in the UV-A region. It is considered that combining a certain UV absorber that is incapable of absorbing a certain UV wavelength region with another UV absorber will provide a UV absorber composition capable of absorbing the whole UV region and also capable of effectively shielding the UV-A region. A primary problem with this approach is that a composition containing UV absorbers different in basic skeleton exhibits poor compatibility with a polymer matrix, often resulting in bleeding or poor solubility in a solvent, which can cause deterioration of the operational efficiency. Another problem is that the differences between the combined UV absorbers in UV shielding effect or rate of degradation with time can cause a failure to obtain sufficient UV shielding effect over the whole UV region.
It has therefore been demanded to develop a UV absorber composition that settles down the above discussed problems and exhibits excellent light resistance even in the UV-A region.